Utilization of point-of-care tests among general practitioners, a cross-sectional study

The base for the structure of the representative questionnaire was an equivalent study from 10 years ago. With the assistance of a GP, a psychologist, and a general practice trainee, this qualified questionnaire was self-designed. The 27 POCTs recorded in the aforementioned earlier study were revised.. PubMed, as well as familiar search engines like Google, and also online suppliers of laboratory supplies, e.g. https://​www.​praxisdienst.​de, have been used for the revision [23].

We selected small and transportable POCTs, that are easily applicable, do not require any additional equipment, and can also be used outside the practice, for example during a home consultation. A further criterium was that the results had to be instantly available (within a few seconds up to 30 min). An easy sample acquisition and processing (using whole blood, urine, saliva, etc.), and uncomplicated storage of materials was also required. For example, due to the large measurement device, we did not select HBA1c POCT.

Based on the above criteria, we included some new POCTs evaluating infectious diseases like Malaria, Syphilis, HIV, and Procalcitonin, such as cardiovascular POCT CK-MB and also POCTs to examine different drugs like INR/Quick for the efficiency of anticoagulation therapy as well as one, not furtherly described Drugtest. BNP was replaced by a NT-proBNP POCT. Obsolete tests have been replaced, namely the Urea breath test, Hydrogen breath test, M2-Pyruvate kinase test, MRSA, Albumin, H1N1 flu, and Salmonella typhii test. A Hydrogen breath test to detect lactose intolerance, for example, is not usable during the home visit because of too long measuring time by five breath tests with a special breath measure test device.

The two-page questionnaire included sociodemographic questions and appraisals about the use and the practicality of 27 POCTs. For each of the 27 tests, four binary questions had to be answered: concerning familiarity of the laboratory parameter, interpretation of this parameter, knowledge about the corresponding POCTs, and whether these POCTs are used. Also, respondents were asked to rate the utility of these tests on a four-point Likert scale: “very useful”, „rather useful “, „rather not useful “,or “not useful”.

A prepaid return envelope, as well as a cover letter declaring the background and the purpose of the study, were attached to each questionnaire.

The questionnaire is available in the appendix.

The sample selection was based on the register of members of the Kassenärztliche Vereinigung Sachsen (Saxon Association of Statutory Health Insurance Physicians KVS, https://​www.​kvs-sachsen.​de; December 2019). In Saxony, the group consisted of 2706 GPs, including specialists for general medicine, internists, and general practitioners without specialist training (“Praktischer Arzt / Ärztin”). To achieve a sufficiently large response rate of 200 to 300 responses, we aimed to write to at least 450 of the 2706 GPs. Thus, we selected a sample of n = 451 GPs, which corresponds to every 6th GP in Saxony. Using a function of the computer program "Microsoft Excel", from 2706 numbers, corresponding to the alphabetically ordered and consecutively enumerated GPs in the list, 451 coincidental numbers were generated. A new lineup of 451 randomly selected GPs appeared. In January 2020, these 451 GPs received the questionnaire in written form. Each potential participant was contacted one time, no pre-warnings or reminders were used. The attendees did not receive any incentives for replying to the questionnaire.

The estimated utility of multiple POCTs was dichotomized in two categories: “(rather) not useful” and “(rather) useful”. Corresponding percentages of GPs, who consider various POCTs as (rather) useful, were depicted in bar charts. All analyses were performed using SPSS Version 25.0 [24].

A total of 451 questionnaires have been sent by mail and 208 have been answered. Due to incomplete replies (a refusal to answer almost every part), two of these questionnaires had to be excluded from further analysis. None of the questionnaires was undeliverable for the reason of incorrect address data. According to the AAPOR standard definition RR2, this consequently issues a response rate of 45.7% [25].

The sociodemographic characteristics of the sample are displayed in Table 1. It consists of a majority of women (64.6%) and has an average age of 52.1 years. These characteristics match the population's distributions. A large part of our individuals operates in solo practices (60.7%), with an average of 18.8 years in practice. In our sample, compared to the population, there are more respondents with academic degree (overrepresentation, p = 0.006) and fewer respondents without medical specialty training (practical physicians) (underrepresentation, p = 0.024).

The questionnaire filed 27 parameters and their relating POCTs. Aggregated replies concerning familiarity and utilization of the 27 POC-tests are presented in Fig. 1. On average, of the 27 parameters reported, primary care physicians knew 20.3 as laboratory parameters and only 9.2 as POCTs. Urine test strips (99.0%), blood glucose test (98.1%), and Troponin I/T (86.4%) were the best known, followed by INR/Quick (82.5%), Microalbumin (79.1%), and D-dimer (78.6%) POCTs. Nevertheless, solely 0 to 13 POC tests were actually used (mean value 4.6). Urine test strips were employed most frequently (97.6%), followed by blood glucose tests (94.7%), Troponin I/T (57.8%), Microalbumin (57.3%), and INR/Quick POCTs (41.7%).

Our results further indicate that known POCTs are also used more frequently. Between utilization and knowledge based on the aggregated proportions, we find a nonparametric correlation of ρ = 0.94; p < 0.01.

The estimated usefulness of POCTs as rather useful or very useful by GPs is demonstrated in Fig. 2. The most frequently considered useful POCTs were Urine test strips (99.5%), Blood glucose (98.5%), Troponin (92.3%), D-dimer (89.5%), and INR/Quick (88.2%). As least useful were ranked Cholesterol (9.9%), Coeliac disease (13.2%), Borrelia (16%) and H-FABP (18.2%) POCTs. At a rate of more than 50% of the respondents, 14 out of 27 POCTs rated as "very useful" or "rather useful" (as cumulative percentages in Fig. 2), and four of them as “very useful” (Blood glucose 92.0%, Urine test strips 91.8%, Troponin I/T 68.5% and INR/Quick 65.7%, not shown in Fig. 2).

The results of POCTs considered most useful largely replicate the findings respecting knowledge and utilization of POCTs.

Due to a random selection from the register of members of the KVS, the sample selection for both studies was done with the same method [22].

Comparing the involved POCTs among the two studies, both included a list of 27 POCTs. Nevertheless, some tests were no longer part of the current study (see method section).

Between the survey carried out almost 10 years ago and the present study, there were some similarities in terms of knowledge, utilization, and estimated usefulness of available and known POCTs [22]. In both surveys, the most famous and most frequently used POCTs were Urine testing strips, Blood glucose, Microalbumin, and Troponin. INR/Quick POCT, which was newly indicluded in the current survey, was also frequently known (82.5%) and used (41.7%), followed by D-dimer, Pregnancy test, CRP, Influenza A & B, and Group A streptococcus POCTs.

This seems to be quite similar to the previous survey 10 years ago and to international data. According to a 2016 study by Sohn et al., US family physicians use POCTs to diagnose diabetes mellitus, urinary tract infections, strep throat, influenza, pregnancy, anemia, infectious mononucleosis, anticoagulation, acute cardiac conditions, and lipid disorders [13].

In general practice, numerous POCTs for diagnosing and monitoring cardiovascular diseases exist, for example, Troponin I/T, NT-proBNP, INR/Quick, D-dimer, and H-FABP. Whereas the majority of the GPs appreciate and use Troponin I/T, D-dimer, and INR/Quick. Within the present survey, it is noteworthy that the D-dimer POCT presents a big difference between knowledge (78.6%) and utilization (35.0%). If the probability is low, D-dimer testing can be helpful to exclude a diagnosis of deep vein thrombosis or pulmonary embolism [20, 26]. Reasons could be concerns about the test accuracy. A positive test result does not have to be thrombosis but can also have other causes so that it is not of much use to the GP in making a diagnosis. NT-proBNP and H-FABP are rarely known and used, in our current survey, as well as in the previous. Some studies are evaluating the efficiency in detecting myocardial damage of patients with acute chest pain, comparing the measurement of high sensitive Troponin I/T and H-FABP. Assessments revealed that the diagnostic value of H-FABP POCT is rather meager and inferior to Troponin I/T POCT [27, 28]. NT-proBNP POCT having been part during the previous survey as BNP POCT, has proven to result in earlier diagnosis, reduced hospitalizations, and seem to be cost-effective for diagnosing and controlling heart failure [29, 30]. However, in our present study, this POCT was rarely known (18.9%) and rarely used (3.9% of GPs). Solely 50.7% of the GPs judged it as useful. One possible reason for the rather poor evaluation could be the cautious recommendations of the AWMF National Health Care Guideline for Chronic Heart Failure of 10/2019. Due to their lower sensitivity, compared to the corresponding laboratory tests, POCTs for BNP and NT-proBNP are not suitable for the exclusion of heart failure without additional transthoracic echocardiography [31].

POCTs for diagnosing infections have become increasingly important for general practice. There exist various POCTs for infectious diseases. We included C-reactive protein, Influenza A and B, Group A streptococcus, Procalcitonin, Helicobacter pylori, Mononukleosis, Respiratory syncytial virus, HIV, Malaria, Chlamydia, Borreliosis, and Syphilis (Fig. 1).

In the prior and the present research, the majority of the GPs knew about the possibility of CRP POCTs. However, only 13.1% currently reported using them (Fig. 1). In a Dutch study, experts favored the CRP POCTs over its laboratory equivalent, as the POCTs allow an instantaneous decision regarding the prescription of antibiotic treatment. 80% of the Dutch GPs declare to use CRP POCTs on a regular basis [5, 32]. CRP POCTs may reduce antibiotic prescribing at the index visit, but there is a higher rate of return visits [33]. In other words, everything has side effects, even POCTs.

Since the questionnaire was sent before the COVID-19 pandemic, it would certainly be interesting to learn whether the present use of CRP and PCT POCTs has increased at first COVID symptoms, such as cough or fever. In addition, PCT POCT has been covered by health insurance since July of 2018. Throughout the next few years, it will probably show whether the current use (just under 2% in our survey) will be increasing due to the recent reimbursement of costs.

Sexually transmitted diseases are still very common in Germany and are associated with significant morbidity and mortality worldwide [34, 35]. There exist multiple POCTs for diagnosing and therapy monitoring. Chlamydia, which was already part of the previous survey, HIV, and Syphilis POCTs, which were newly included, showed low familiarity and usage rate. Only HIV POCT were rated as useful by 45.4% of GPs. These tests offer the advantage of a prompt diagnosis, allowing immediate treatment and a reduction of disease transmission [36]. In our current survey, POCT is strongly recommended in German guidelines and is expected to increase in the future [37, 38].

GPs have common concerns on the reliability of the POCTs and the comparability to central laboratory results, over-reliance on tests, usage without appropriate indication, and uncertain use and interpretation [1]. Besides, very often the staff needs to be trained and/ or taught about the handling of the POCT. The relatively meager billing option might be an additional argument why German physicians do not employ them [39]. Influenza POCTs, for example, are generally recommended by the Robert Koch Institute but are not reimbursed by German legal health insurances [40].

Some of the POCTs require an appropriate storage which might be costly. An additional concern of the GPs is that POCTs do not guarantee an improved patient outcome [1, 5, 21].

An inference of Deutsches Ärzteblatt from 2017 stated that POCTs should only be employed with extreme caution. Limitations in terms of sensitivity, specificity, and cost-effectiveness should always be weighed against the available quality-assured laboratory diagnostics [41]. As most POCTs have not been sufficiently evaluated, Schols et al. also recommend that GPs should remain critical of which tests they order [1].

Throughout the usage of POCTs, the practice location seems to play a role. The previous survey affirmed a difference in the knowledge, but not regarding the utilization of POCTs between rural GPs and their urban colleagues. As a result, we did not newly investigate this [22]. A study from the UK did not reveal any correlation concerning the demographic data neither [22, 42]. However, this could play a role in resource-limited environments [43].

The current study examines a coincidental sample from a limited list of all registered general practitioners in Saxony. The representativeness criterion and the connection with the satisfactory response rate of 46.1% can be seen as a strength of the present survey. Yet, to obtain more responses a timely reminder would have been advantageous. The sample solely represents 208 of the 2706 GPs in Saxony—representing 7.6% of the target population in only one geographical area in Germany. That, being said, could be considered a weakness.

The self-administered pen-and-pencil questionnaire was modified and improved several times. Eventually, there was a pre-test by a GP in private practice without complaints. For comparability, we employed a tried and tested questionnaire with a commonly intelligible structure similar to the one ten years ago, so we abstained from a pilot-test.

In addition, there is evidence of an overrepresentation of respondents with an academic dregee and an underrepresentation of GPs without specialist medical training. Possible motives for these biases in response behavior are workload within the practice, specific interest in the topic of the survey, or in university research in general. These characteristics are presumed confounders with regards to the usage of POCTs and impose the relevant limitations on the generalizations of our results.

Impacts on social usefulness, e.g., an over-reporting on the level of knowledge and utilization of POCTs, cannot be excluded. Bias from some inadequately completed questionnaires is also possible. Some laboratory or POC tests were totally disregarded, leaving entire lines, and even rarely, entire sections unfilled, so-called unit non-response. Whether the GPs were merely oblivious of the POCTs or deliberately did not answer cannot be differentiated. Altogether, we excluded 2 of these inadequately completed questionnaires from the analysis. Also, we connot differentiate how often respondents use the POCT when they indicate using it. In addition, we included a 4-point Likert scale where participants could choose if a POCT was (very) useful or not (very) useful. There existed no other response options such as „I am unsure “. The use of only four categories limits the validity. Compared to the previous survey, the current representation solicited different GPs. Therefore, longitudinal comparisons on familiarity and usage of POCTs have analogous limitations. Moreover, the present questionnaire did not investigate the clinical syndromes for which the POCTs are used. As POCTs are most likely to be considered useful in the context of diabetes, this creates a further constraint [42].

The questionnaire did not examine motives why the GPs might estimate the tests as rather not utile, nor did it investigate possible concerns that might prevent GPs from using the existing POCTs. In order to improve the utilization of POCTs in general practice, further research should assess this. Due to the heterogeneous health systems, diverse limitations may arise.

Another significant characteristic affecting the employment of POCTs involves their size and portability; particularly with respect to the distinction between bedside and near-bedside POCTs [44]. The present questionnaire only considered portable POCTs with small devices, which are appropriate for home visits. Yet, further research should approach the utilization and the perceived utility of near-bedside POCTs.